Finger biometric sensor including stacked die each having a non-rectangular shape and related methods

ABSTRACT

A finger biometric sensor may include first and second integrated circuit (IC) dies arranged in a stacked relation. The first IC die may include a first semiconductor substrate and an array of finger biometric sensing pixels thereon, and the second IC die may include a second semiconductor substrate and processing circuitry thereon coupled to the array of finger biometric sensing pixels. The first and second IC dies may each have respective first and second non-rectangular shapes, such as circular shapes that are coextensive.

FIELD OF THE INVENTION

The present invention relates to the field of electronics, and, moreparticularly, to finger sensing devices and related methods.

BACKGROUND OF THE INVENTION

Fingerprint sensing and matching is a reliable and widely used techniquefor personal identification or verification. In particular, a commonapproach to fingerprint identification involves scanning a samplefingerprint or an image thereof and storing the image and/or uniquecharacteristics of the fingerprint image. The characteristics of asample fingerprint may be compared to information for referencefingerprints already in a database to determine proper identification ofa person, such as for verification purposes.

A particularly advantageous approach to fingerprint sensing is disclosedin U.S. Pat. No. 5,953,441 to Setlak and assigned to the assignee of thepresent invention, the entire contents of which are herein incorporatedby reference. The fingerprint sensor is an integrated circuit sensorthat drives the user's finger with an electric field signal and sensesthe electric field with an array of electric field sensing pixels on theintegrated circuit substrate.

A particularly advantageous approach to multi-biometric fingerprintsensing is disclosed in U.S. Pat. No. 7,361,919 to Setlak, which isassigned to the assignee of the present invention and is incorporated inits entirety by reference. The Setlak patent discloses a multi-fingersensing device sensing different biometric characteristics of a user'sfinger that have different matching selectivities.

A fingerprint sensor may be particularly advantageous for verificationand/or authentication in an electronic device, and more particularly, aportable device, for example. Such a fingerprint sensor may be carriedby the housing of a portable electronic device, for example, and may besized to sense a fingerprint from a single-finger. Thus, a fingerprintsensor may be particularly advantageous for providing more convenientaccess to the electronic device without a password, for example, and,more particularly, without having to type the password, which is oftentime consuming. A fingerprint sensor may also be particularlyadvantageous for starting one or more applications on the electronicdevice.

U.S. Patent Application Publication No. 2011/0175703 to Benkley, IIIdiscloses an electronic imager using an impedance sensor grid arraymounted on or about a switch. More particularly, Benkley, III disclosesa switch being incorporated into a sensor assembly that allowsintegration of sensor operations, such as, fingerprint sensoroperations. A fingerprint sensor can be used for authentication whilebeing used together with a power switch or navigation selection switch.The authentication may be used to access the device entirely or accessdifferent levels of information.

While a fingerprint sensor used in an electronic device may beparticularly advantageous for authentication, navigation, etc., it maybe desirable that these sensors have a reduced size to accommodate therelatively small amount of space available on the housing of theportable electronic device. However, making a fingerprint sensor smallermay make it less accurate because a smaller sensing area is available.Thus, processing time may be increased.

SUMMARY OF THE INVENTION

In view of the foregoing background, it is therefore an object of thepresent invention to provide a finger biometric sensor for occupyingless area in an electronic device and/or fitting a particular geometry,while maintaining accuracy and processing speed.

This and other objects, features, and advantages in accordance with thepresent invention are provided by a finger biometric sensor that mayinclude first and second integrated circuit (IC) dies arranged in astacked relation. The first IC die may include a first semiconductorsubstrate and an array of finger biometric sensing pixels thereon. Thesecond IC die may include a second semiconductor substrate andprocessing circuitry thereon coupled to the array of finger biometricsensing pixels. The first and second IC dies may each have respectivefirst and second non-rectangular shapes. Accordingly, the fingerbiometric sensor may provide a smaller package size, particularly for anon-rectangular shape, and with a reduced impact or no impact onaccuracy and processing speed. For example, by moving processingcircuitry typically located adjacent the finger biometric sensing pixelsto another stacked die, the finger biometric sensor may be reduced insize.

The first and second non-rectangular shapes may include respective firstand second closed curve shapes. For example, the first and secondnon-rectangular shapes may include respective first and second circularshapes.

The array of finger biometric sensing pixels may extend to adjacent aperiphery of the first semiconductor substrate. The first and secondnon-rectangular shapes may be coextensive, for example.

The first IC die may include a plurality of electrically conductive viasextending therethrough and coupling the array of finger biometricsensing pixels and the processing circuitry. The processing circuitrymay include pixel addressing circuitry and at least one gain stagecoupled thereto, for example.

The finger biometric sensor may further include a top dielectric layeroverlying the array of finger biometric sensing pixels. The fingerbiometric sensor may also include a dielectric sidewall extendingdownwardly from the top dielectric layer and surrounding the first andsecond IC dies. The array of finger biometric sensing pixels may includean array of electric field sensing pixels, for example.

An electronic device aspect is directed to an electronic device that mayinclude a housing and the finger biometric sensor carried by thehousing. The electronic device may include a wireless transceiver and aprocessor capable of cooperating therewith to perform at least wirelesscommunications function. The electronic device may further include afinger-operated input device carrying the plurality of die, for example.

A method aspect is directed to a method of making a finger biometricsensor. The method may include forming a first integrated circuit (IC)die that may include a first semiconductor substrate and an array offinger biometric sensing pixels thereon. The method may further includeforming a second IC die that may include a second semiconductorsubstrate and processing circuitry thereon to be coupled to the array offinger biometric sensing pixels. The method may also include arrangingthe first and second IC dies in a stacked relation. The first and secondIC dies may each have respective first and second non-rectangularshapes.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of an electronic device according to the presentinvention.

FIG. 2 is a schematic block diagram of the electronic device of FIG. 1including a portion of a finger biometric sensor in accordance with thepresent invention.

FIG. 3 is a more detailed schematic diagram of a portion of the fingerbiometric sensor of FIG. 2.

FIG. 4 is a schematic diagram of a portion of a hexagonal shaped fingerbiometric sensor according to another embodiment of the presentinvention.

FIG. 5 is a schematic diagram of a portion of an octagonal shaped fingerbiometric sensor according to another embodiment of the presentinvention.

FIG. 6 is a schematic diagram of a portion of an oval shaped fingerbiometric sensor in according to another embodiment of the presentinvention.

FIG. 7 is a schematic block diagram of an electronic device including afinger biometric sensor according to another embodiment of the presentinvention.

DETAILED DESCRIPTION

The present embodiments will now be described more fully hereinafterwith reference to the accompanying drawings. These embodiments may,however, have in many different forms and should not be construed aslimited to the embodiments set forth herein. Rather, these embodimentsare provided so that this disclosure will be thorough and complete. Likenumbers refer to like elements throughout, and prime and multiple primenotation, and reference numerals in increments of 100 are used to referto similar elements in different embodiments.

Referring initially to FIGS. 1 and 2, an electronic device 20 is nowdescribed. The electronic device 20 illustratively includes a portablehousing 21, and a processor 22 carried by the portable housing. Theelectronic device 20 is illustratively a mobile wireless communicationsdevice, for example, a cellular telephone. The electronic device 20 maybe another type of electronic device, for example, a tablet computer,laptop computer, etc.

A wireless transceiver 25 (e.g. cellular, WLAN Bluetooth, etc.) is alsocarried within the housing 21 and coupled to the processor 22. Thewireless transceiver 25 cooperates with the processor 22 to perform atleast one wireless communications function, for example, for voiceand/or data. In some embodiments, the electronic device 20 may notinclude a wireless transceiver 25.

A display 23 is also carried by the portable housing 21 and is coupledto the processor 22. The display 23 may be a liquid crystal display(LCD), for example, or may be another type of display, as will beappreciated by those skilled in the art. A memory 26 is also coupled tothe processor 22.

A finger-operated user input device, illustratively in the form of apushbutton switch 24, is also carried by the portable housing 21 and iscoupled to the processor 22. The pushbutton switch 24 cooperates withthe processor 22 to perform a device function in response to thepushbutton switch. For example, a device function may include a poweringon or off of the electronic device 20, initiating communication via thewireless communications circuitry 25, and/or performing a menu function.

More particularly, with respect to a menu function, the processor 22 maychange the display 23 to show a menu of available applications basedupon pressing of the pushbutton switch 24. In other words, thepushbutton switch 24 may be a home switch or button, or key. Of course,other device functions may be performed based upon the pushbutton switch24. In some embodiments, the finger-operated user input device may be adifferent type of finger-operated user input device, for example,forming part of a touch screen display. Other or additionalfinger-operated user input devices may be carried by the portablehousing 21.

A finger biometric sensor 30 is carried by the pushbutton switch 24 tosense a user's finger 40 placed adjacent the finger biometric sensor.The finger biometric sensor 30 is carried by the pushbutton switch 24 sothat when a user contacts and/or presses downward on the pushbuttonswitch, data from the user's finger 40 is acquired, for example, forfinger matching and/or spoof detection, as will described in furtherdetail below. In other words, the finger biometric sensor 30 may beresponsive to static contact or placement of the user's finger 40 orobject. Of course, in other embodiments, for example, where the fingerbiometric sensor 30 is not carried by a pushbutton switch, the fingerbiometric sensor may be a slide sensor and may be responsive to slidingcontact, or the finger biometric sensor may be a standalone staticplacement sensor.

Referring now additionally to FIG. 3, the finger biometric sensor 30includes first and second integrated circuit (IC) dies 31, 32 arrangedin a stacked relation. The first IC die 31 includes a firstsemiconductor substrate 33 and an array of finger biometric sensingpixels thereon 34. More particularly, the array of finger biometricsensing pixels 34 are carried by an upper surface of the firstsemiconductor substrate 33. The array of finger biometric sensing pixels34 illustratively extends to a periphery of the upper surface of thefirst semiconductor substrate 33. The array of finger biometric sensingpixels 34 are electric field sensing pixels, such as, for example, asdescribed in U.S. Pat. No. 5,940,526 to Setlak at al., assigned to thepresent assignee, and the entire contents of which are hereinincorporated by reference.

The second IC die 32 includes a second semiconductor substrate 35.Processing circuitry 36 is carried on the second semiconductor substrate35 and is coupled to the array of finger biometric sensing pixels 34.More particularly, the processing circuitry 36 may include pixeladdressing circuitry 37 and one or more gain stages 38 coupled thereto.For example, the pixel addressing circuitry 37 may be for addressingrows and/or columns for addressing the pixels. The gain stage 37 mayinclude one or more amplifiers, for example, one or more senseamplifiers with gain, as will be appreciated by those skilled in theart.

The first and second IC dies 31, 32 each have respective first andsecond non-rectangular shapes. In particular, the first and second ICdies 31, 32 each have respective first and second closed curve shapes,illustratively, a circular shape. Of course, in some embodiments, thefirst and second dies 31, 32 may each have other non-rectangular shapes,such as, for example, a polygon having a number of sides greater thanfour, e.g., hexagonal, octagonal, etc. In particular, as illustrated inFIG. 4, the array of finger biometric sensing pixels 134 is carried bythe first semiconductor substrate 133 of a hexagonal shaped first die131. FIG. 5 illustrates the array of finger biometric sensing pixels 234being carried by the first semiconductor substrate 233 of an octagonalshaped first die 231.

In some embodiments, the non-rectangular shape may also be a closedcurve, such as an oval. For example, as illustrated in FIG. 6, the arrayof finger biometric sensing pixels 334 is carried by the firstsemiconductor substrate 333 of an oval shaped first die 331.

The non-rectangular shapes of the first and second first and second dies31, 32 are coextensive. For example, the first and second IC dies 31, 32may have the same shape and may also be aligned as shown. Of course, inother embodiments, the non-rectangular shapes of the first and second ICdies 31, 32 may not be coextensive and may not be aligned. For example,the second IC die 32 may be larger (i.e., surface area) than the firstIC die 31.

The first IC die also includes electrically conductive vias 41 a-41 nextending therethrough. The electrically conductive vias 41 a-41 ncouple the array of finger biometric sensing pixels 34 and theprocessing circuitry 36. In some embodiments, the electricallyconductive vias 41 a-41 n may be through-silicon vias (TSVs), forexample. Of course, in other embodiments, the electrical connections maybe provided by other arrangements, as will be appreciated by thoseskilled in the art.

A top dielectric layer 42 illustratively overlays the array of fingerbiometric sensing pixels 34. A dielectric sidewall 43 extends downwardlyfrom the top dielectric layer 42 and surrounds the first and second ICdies 31, 32. The top dielectric layer 42 and sidewall 43 may provideincreased protection of the array of finger biometric sensing pixels 34,and/or may be used for aesthetics. In other words, the top dielectriclayer 42 and sidewall 43 may be part of the pushbutton assembly. Itshould be understood that the dielectric top layer 42 is not thepassivation layer of the first IC die 31. The finger biometric sensor 30may include other and/or additional layers.

Referring now to FIG. 7, in some embodiments, the finger biometricsensor 30′ may also include drive circuitry 44′ coupled to the array offinger biometric sensing pixels 34′ and a finger coupling electrode 45′adjacent the array of electric field sensing pixels and coupled to thedrive circuitry. The array of finger biometric sensing pixels 34′ maycooperate with drive circuitry 44′ to couple the user's finger 40′ to areference and generate a detected signal based upon placement of theuser's finger adjacent the array of finger biometric sensing pixels, aswill be appreciated by those skilled in the art. Further details ofexample drive circuitry 44′ and finger coupling electrode are describedin U.S. Pat. No. 5,963,679, to Setlak and assigned to the presentassignees, and the entire contents of which are herein incorporated byreference.

Alternatively, the finger biometric sensor 30 may not include a fingercoupling electrode, but rather the finger biometric sensing pixels 34may be operated in one of a transmitting mode for transmitting RF intothe user's finger and a sensing mode for receiving finger biometricdata. In other words, the processing circuitry 36, and moreparticularly, the pixel addressing circuitry 37 may operate some fingerbiometric finger sensing pixels in the transmitting mode while operatingothers in the receiving mode. Further details of operating the fingerbiometric sensing pixels in the transmitting and receiving modes aredescribed in U.S. Application Publication No. 2011/0122059 to Guerreroet al., and assigned to the assignee of the present application, and theentire contents of which are herein incorporated by reference.

In some embodiments, the processor 22 may cooperate with the fingerbiometric sensor 30 to perform an authentication function. For example,the processor 22 may cooperate with the cooperate with the fingerbiometric sensor 30 to perform a matching operation between enrolledfinger biometric data stored in the memory 26 and finger biometric dataacquired from the finger biometric sensor 30. The processor 22 may alsocooperate with the finger biometric sensor to perform a spoof detectionfunction, for example. For example, the processor 22 may cooperate withthe finger biometric sensor 30 to determine whether an object adjacentthe array of finger biometric sensing pixels 34 is indicative of hascharacteristics of a spoof finger. Of course, the processor 22 maycooperate with the finger biometric sensor 30 to perform other and/oradditional functions, as will be appreciated by those skilled in theart.

As will be appreciated by those skilled in the art, the finger biometricsensor 30 may be particularly advantageous for use in an electronicdevice where it may be desirable to have a non-rectangular shape andreduced size relative to prior art finger biometric sensors. Forexample, reducing the size of a finger biometric sensor reduces theamount of finger biometric sensing pixels, which in turn may reduceaccuracy and increase processing time. This may be particularly true fora non-rectangular shaped finger biometric sensors. By moving processingcircuitry typically located adjacent the finger biometric sensing pixelsto another stacked die a reduced number of a finger biometric sensingpixels may be affected when reducing the size of the finger biometricsensor. Additionally, by extending the finger biometric pixels to aperiphery, or where the processing circuitry was once located, impact onaccuracy and processing speed may be further reduced.

Based upon increased area available on the second IC die 32, forexample, the processing circuitry 36 may be capable or additionalfunctions. For example, the processing circuitry 36 may perform orintegrate key security, image processing and matching functions.Additionally, overall system security may improve because encryptionkeys and fingerprint template information may be increasingly difficultto get “hacked” from the outside world. By including the fingerprintmatching functions “on chip” or on the second die 32, for example, mayfacilitate a power on authentication mode, which may place theprocessing circuitry 36 in a low power state. Overall processing timemay also be reduced, which corresponds to reduced response times withrespect to the user. Still further, the increased area on the second die32 may be particularly suited for specialized processes, for example,high voltage processes, that may be targeted for the bottom die, whichmay assist the integration of module components, such as, for example,regulators, high voltage booster circuits, and decoupling components.This may further reduce component cost and reduce assembly complexityand related issues, as will be appreciated by those skilled in the art.

A method aspect is directed to a method of making a finger biometricsensor 30. The method includes forming a first integrated circuit (IC)die 31 that may include a first semiconductor substrate 33 and an arrayof finger biometric sensing pixels 34 thereon. The method also includesforming a second IC die 32 that includes a second semiconductorsubstrate 35 and processing circuitry 36 thereon to be coupled to thearray of finger biometric sensing pixels 34. The method also includesarranging the first and second IC dies 31, 32 in a stacked relation. Thefirst and second IC dies 31, 32 each have respective first and secondnon-rectangular shapes.

Many modifications and other embodiments of the invention will come tothe mind of one skilled in the art having the benefit of the teachingspresented in the foregoing descriptions and the associated drawings.Therefore, it is understood that the invention is not to be limited tothe specific embodiments disclosed, and that modifications andembodiments are intended to be included within the scope of the appendedclaims.

That which is claimed is:
 1. A finger biometric sensor comprising: firstand second integrated circuit (IC) dies arranged in a stacked relation;said first IC die comprising a first semiconductor substrate and anarray of finger biometric sensing pixels thereon; said second IC diecomprising a second semiconductor substrate and processing circuitrythereon coupled to said array of finger biometric sensing pixels; saidfirst and second IC dies each have respective first and secondnon-rectangular shapes.
 2. The finger biometric sensor according toclaim 1 wherein the first and second non-rectangular shapes compriserespective first and second closed curve shapes.
 3. The finger biometricsensor according to claim 1 wherein the first and second non-rectangularshapes comprise respective first and second circular shapes.
 4. Thefinger biometric sensor according to claim 1 wherein said array offinger biometric sensing pixels extend to adjacent a periphery of saidfirst semiconductor substrate.
 5. The finger biometric sensor accordingto claim 1 wherein the first and second non-rectangular shapes arecoextensive.
 6. The finger biometric sensor according to claim 1 whereinsaid first IC die comprises a plurality of electrically conductive viasextending therethrough and coupling said array of finger biometricsensing pixels and said processing circuitry.
 7. The finger biometricsensor according to claim 1 wherein said processing circuitry comprisespixel addressing circuitry and at least one gain stage coupled thereto.8. The finger biometric sensor according to claim 1 further comprising atop dielectric layer overlying said array of finger biometric sensingpixels, and a dielectric sidewall extending downwardly from said topdielectric layer and surrounding said first and second IC dies.
 9. Thefinger biometric sensor according to claim 1 wherein said array offinger biometric sensing pixels comprises an array of electric fieldsensing pixels.
 10. An electronic device comprising: a housing; a fingerbiometric sensor carried by said housing and comprising first and secondintegrated circuit (IC) dies arranged in a stacked relation; said firstIC die comprising a first semiconductor substrate and an array of fingerbiometric sensing pixels thereon; said second IC die comprising a secondsemiconductor substrate and processing circuitry thereon coupled to saidarray of finger biometric sensing pixels; said first and second IC dieseach have respective first and second non-rectangular shapes.
 11. Theelectronic device according to claim 10 wherein the first and secondnon-rectangular shapes comprise respective first and second closed curveshapes.
 12. The electronic device according to claim 10 wherein thefirst and second non-rectangular shapes comprise respective first andsecond circular shapes.
 13. The electronic device according to claim 10wherein said array of finger biometric sensing pixels extend to adjacenta periphery of said first semiconductor substrate.
 14. The electronicdevice according to claim 10 wherein the first and secondnon-rectangular shapes are coextensive.
 15. The electronic deviceaccording to claim 10 further comprising a wireless transceiver and aprocessor capable of cooperating therewith to perform at least onewireless communications function.
 16. The electronic device according toclaim 10 further comprising a finger-operated input device carrying saidfinger biometric sensor.
 17. A method of making a finger biometricsensor comprising: forming a first integrated circuit (IC) diecomprising a first semiconductor substrate and an array of fingerbiometric sensing pixels thereon; forming a second IC die comprising asecond semiconductor substrate and processing circuitry thereon to becoupled to the array of finger biometric sensing pixels; and arrangingthe first and IC dies in a stacked relation, the first and second ICdies each have respective first and second non-rectangular shapes. 18.The method according to claim 17 wherein the first and secondnon-rectangular shapes comprise respective first and second closed curveshapes.
 19. The method according to claim 17 wherein the first andsecond non-rectangular shapes comprise respective first and secondcircular shapes.
 20. The method according to claim 17 wherein formingthe first IC die comprises forming the array of finger biometric sensingpixels to extend adjacent a periphery of the first semiconductorsubstrate.
 21. The method according to claim 17 wherein the first andsecond non-rectangular shapes are coextensive.
 22. The method accordingto claim 17 further comprising positioning a top dielectric layer tooverlay the array of finger biometric sensing pixels, and a dielectricsidewall to extend downwardly from the top dielectric layer andsurrounding the first and second IC dies.